UFOs are real, says the Department of Defense, and while that doesn't mean that aliens have definitely visited Earth, we're going to keep our hopes up. We've still got movies as a way to experience encounters with extra-terrestrial life. The greatest science fiction movies have given form to our dreams and fears about meeting life from beyond the bounds of Earth; some of the run-ins in the best alien movies are even friendly!

From the beautiful story in E.T.: THE EXTRA-TERRESTRIAL to the bio-mechanical terror of ALIEN, here are the seven best movie aliens we've ever seen.

The story of a lost alien who tries to use Earth's primitive technology in order to reunite with their kind and return home is one of Steven Spielberg's greatest achievements. Though E.T. is not actually scary, Spielberg's storytelling has the air of early pulp sci-fi, which was always close to horror. It helps that the design in Spielberg's movie — created by the late Carlo Rambaldi, who also created aliens for CLOSE ENCOUNTERS OF THE THIRD KIND and did the wild Guild Navigator design for David Lynch's DUNE — is an outlier in the realm of sci-fi movie aliens. E.T. does not look like a person in an alien suit. It truly looks like a being from somewhere far beyond Earth's atmosphere. The movie that reveals the alien so convincingly portrays childhood wonder and discovery that we accept the strange visitor at face value — and quickly come to accept and love him.

John McTiernan's movie helped define '80s action thanks to the presence of stars Arnold Schwarzenegger and Carl Weathers, not to mention the muscular support from Bill Duke, Richard Chaves, and Jesse Ventura. The story is simple, the action is clear, and the characters are memorable. All that is before we even take into account the Predator itself — and that alien hunter is a masterpiece of icky/impressive creature design. With a full complement of exotic weaponry, an off-putting helmet and that face, which looks like a cross between a bug and some ancient crustacean, the Predator is an unforgettable example of near-perfect design. And just think: It could have been Jean-Claude van Damme bouncing around the jungle in a rubber suit instead!

The novel by H.G. Wells is famous as a foundational science fiction classic; the 1938 radio adaptation by Orson Welles is infamous. There are seven movie versions of WAR OF THE WORLDS, many of which have very cool visions of the alien tripods which try to dominate Earth in order to control its water. None, however, are as overwhelmingly convincing — and as ultimately terrifying — as those in Steven Spielberg's 2005 movie version. These towering tripods are devious and ruthless when encountered on their own and overwhelmingly powerful in packs. They scour the landscape and reduce cities to rubble. And yet they remain vulnerable to some of the simplest life on Earth, and we get to remain hopeful that technology will not be the most important aspect of an eventual encounter with alien life.

Sometimes the best way to create amazing movie aliens is to suggest that they might already be among us, living in secret and biding their time. Granted, this movie's visitors — gooey life forms which land on Earth after escaping their own dying planet — don't wait very long before staging a takeover. These aliens are visualized as giant, bizarre pods which bear almost undetectable replicas of human beings. The pods are creepy, but the inhuman behavior of the plant-like people they spit out are even more unnerving. INVASION OF THE BODY SNATCHERS is a big allegory, of course, but the idea of people being replaced by unfeeling aliens is such a pure concept that "pod person" quickly became a quick way of describing unusual or impersonal behavior. With a hard-working cast that includes Brooke Adams, Leonard Nimoy, Jeff Goldblum, Veronica Cartwright, Art Hindle, and, most famously, Donald Sutherland, the threat imagined by these aliens seems very real indeed.

In ARRIVAL, aliens hover in the skies above major cities on Earth. Why are they here? What do they want? Heck, what are they? The creature design in this movie is impressive; the visitors are almost Lovecraftian visions of strangeness that glide forward and back in big mist-filled tanks. Each one is like a giant squid that walks on something that is almost a hand. They communicate with swirls of dark gas, and their language is a gateway to an understanding of time that is far beyond normal human experience. They are frightening, to be sure, but there's something almost hopeful about them, too, as contact with these beings leads one woman to a more peaceful understanding of her own life, even in its worst moments.

Like INVASION OF THE BODY SNATCHERS, John Carpenter's remake of a '50s sci-fi classic is all about paranoia and unseen threats. Unlike BODY SNATCHERS, however, Carpenter and special effects artist Rob Bottin make sure we get to see the creature in several super-gnarly forms. An American research station in Antarctica becomes the incubation environment for a shape-changing visitor from space after a nearby Norwegian research crew digs up a long-buried craft from outer space. The alien arrives in the form of a dog, then quickly mutates into human form, as seen in several gory, gooey setpieces. The lack of a single shape for this thing is precisely what makes it scary. When characters played by Kurt Russell and Keith David are totally freaked out when trying to deal with this creature, how can we maintain our own composure?

Ridley Scott's "truckers in space" movie is a blue-collar nightmare in which a bunch of workers are given up as fodder for the ambitions of their employer — and that's even before we get to the amazing alien. The so-called xenomorph gives us not one but three incredible creatures in one. There's the hand-shaped egg-laying "facehugger," which might be the most frightening idea in the movie, then the newly-hatched alien, which is born in one of the most gruesome scenes we've ever witnessed. The full-grown alien is like several nightmares combined into one. Is it alive, or mechanical? Why does it have a tongue with teeth? How did it get so big — and so smart? Though played by an actor, Bolaji Badejo, in many scenes, this alien seems as far from human as it is possible to be. It is a triumph of H.R. Giger's design and Ridley Scott's direction, combined with incredible suit construction and the coordination of puppetry and special effects. Four decades later, it still haunts us, making us think that maybe it's best not to actually meet aliens after all.

Check out the movies now playing at Cinemark!

All images courtesy of Universal Pictures, unless otherwise indicated.